neuron
mass of nerve cells; structural and functional unit of nervous system; specialized to react to physical and chemical changes in their surroundings; transmits info in the form of electrochemical changes (nerve impulses) to other neurons and to cells outsid
nerve impulse
information in form of electrochemical change (transmitted by neurons)
cell body
rounded area of neuron
dendrites
numerous extensions from cell body; receive electrochemical messages
axon
extensions that send information in the form of nerve impulses
nerve
bundle of axons
neuroglial cells
provide physical support, insulation and nutrients for neurons; included in nervous tissue alongside nerves
CNS
brain and spinal cord
PNS
connects CNS to other body parts
sensory receptors
located at the ends of peripheral neurons; performs sensory functions; gather info by detecting changes inside and outside body; convert info into nerve impulses, which are then transmitted over peripheral nerves to the CNS
peripheral neurons
carry impulses from CNS to responsive structures called effectors
effectors
muscles/glands that are stimulated by nerve impulses (brought from the CNS by peripheral neurons)
somatic ns
controls skeletal muscle
autonomic ns
controls involuntary effectors, like the heart
myelin
electrical insulator produced by neuroglial cells (specifically oligodendrocytes)
microglial cells
type of neuroglial cells; scattered throughout CNS; support neurons and phagocytize bacterial cells and cellular debris
astrocytes
type of neuroglial cells; commounly found between neurons and blood vessels; provide structural supports, join parts by their abundant cellular processes, help regulate concentrations of nutrients and ions within tissue
oligodendrocytes
type of neuroglial cells; align along nerve fibers; provide myelin (around axons within brain and spinal cords); does not provide neurilemma, so CNS neurons can't regenerate
ependymal cells
type of neuroglial cells; form epithelia-like membrane that covers specialized brain parts and forms inner linings that enclose spaces within brain and spinal cord
Schwann cells
type of neuroglial cells; forms myelin sheath around axons of PNS; provide neurilemma, so PNS axons can regenerate
nodes of Ranvier
narrow gaps between Schwann cells on axons of PNS
gray matter
unmyelinated axons and neuron cell bodies within CNS
white matter
myelinated axons of CNS (white in appearance)
multipolar neuron
neuron with many processes arising from their cell bodies; only one process is axon; rest are dendrites; most have cell bodies that lie within brain or spinal cord
bipolar neuron
neuron with only two processes, one from each end of cell body; normally found in eyes, nose and ears
unipolar neurons
single process extending from cell body (essentially just an axon); one is peripheral process (technically dendrites) and other is central process (which enters brain or spinal cord); reach outside brain/spinal cord; aggregate in specialized masses called
sensory neurons
carry nerve impulses from peripheral body parts into brain/spinal cord; either have specialized receptor ends at tips of dendrites, or are closely associated with receptor cells; most are unipolar (but some are bipolar)
interneurons
lie entirely within brain/spinal cod; multipolar; transmit impulses from one part of brain/spinal cord to another
motor neurons
multipolar; carry nerve impulses out of brain/spinal cord to effectors (muscles/glands)
synapse
junction between any two communicating neurons
synaptic cleft
gap between neurons
presynaptic neuron
sender neuron
postsynaptic neuron
receiver neuron
synaptic transmission
process of crossing synaptic cleft with impulse
neurotransmitters
biochemicals that carry out synaptic transmission; ex: acetylcholine; released by synaptic vesicles when impulse reaches synaptic knob (triggered by calcium influx through then opened channels); then diffuses across synaptic cleft and reacts with specific
action potential
characteristic change in neuron membrane polarization and return to the resting state forms a nerve impulse that is propagated along an axon
potassium
passes through cell membrane much more easily than sodium; results in negative charge within cell
resting potential
potential difference between negative inside of neuron and positive outside of neuron
calcium
responsible for allowing the release of acetylcholine, which then opens sodium channels in postsynaptic neuron (allowing for action potential to transfer)